The objectives of the Registry of Experimental Cancers are the storage and retrieval of pathologic material and data on cancers and other lesions of laboratory animals (primarily rodents) and the use of such information for research and educational purposes. The Registry has acquired a total of 2,396 (177 since the 1983 report) single or group accessions from investigators outside the NCI and approximately 59,602 records have been coded. Thirty-five investigators have come to the Registry for study and consultation on single or multiple visits.